Rotary radial-piston machine



1964 E. KAUERTZ 3,144,007

ROTARY RADIAL-PISTON MACHINE Filed June 28, 1961 7 Sheets-Sheet 1 I992 I 7 A 6 7 5 EUGEN KAUERTZ Inventor? 1964 E. KAUER'fZ 3,144,007

ROTARY RADIAL-PISTON MACHINE 7 Sheets-Sheet 2 Filed June 28, 1961 EUGEN KAUERTZ .fm/emorz' Aug. 11, 1964 E. KAUERTZ ROTARY RADIAL-PISTON MACHINE 7 Sheets-Sheet 3 Filed June 28, 1961 EUGEN KAUERTZ jflvenzon' Aug. 11, 1964 E. KAUERTZ 3,144,007

ROTARY RADIAL-PISTON MACHINE Filed June 28. 1961 7 Sheets-Sheet 4 EUGEN KAUERTZ .lm/errzon- E. KAUERTZ ROTARY RADIAL-PISTON MACHINE Aug. 11, 1964 7 Sheets-Sheet 5 Filed June 28, 1961 EUGEN KAURTZ m/emon' Augrll; 1964 v EJKAUERTZ 4 0 ROTARYRADIAL-PISTON MACHINE filed June 28, 1961 7 Sheets-Sheet 6 EU GE N KAUERTZ a (7 4 QM Aug. 11, 1964 E. KAUERTZ ROTARY RADIALPISTON MACHINE '7 Sheets-Sheet 7 Filed June 28, 1961 S B ED Ea EUGEN KAUERTZ IN VEN TOR United States Patent 3,144,007 ROTARY RADIAL-PISTON MACHINE Eugen Kaucrtz, Kraheck, Germany, assignor to Kauertz (Proprietary) Limited, Transvaal Province, Republic of South Africa, a limited-liability company of the Republic of South Africa Filed June 28, 1961, Ser. No. 120,431 Claims priority, application Germany June 29, 1960 6 Claims. (Cl. 123-11) My present invention relates to rotary radial-piston machines and, more particularly, to radial-piston internalcombustion engines.

Radial-piston or radial-vane internal-combustion engines are known wherein at least two pairs of diametrically opposite radial vanes are secured to common shafts and constitute double-vane pistons rotatable concentrically within a common cylinder, yet such machines generally have heretofore been equipped with complicated linkages for the necessary relative angular displacement of the two pairs of vanes. These linkages, adapted periodically to enlarge and contract the chambers formed between the two pistons, usually were sliding-crank devices of inordinate complexity involving considerable power losses 0wing to sliding friction between the crank elements, there by resulting in the deterioration and severe wear of the slidingly engageable crank parts. Moreover, devices incorporating the sliding-crank linkages were unable to gain wide-spread acceptance owing, at least in part, to the inefliciency of such linkages and the resulting kinematic relationship between the two double-vane pistons designed alternately to accelerate and to brake the two pistons for periodic enlargement and contraction of the working chambers of these devices to the requisite extent. The output of sliding-crank rotary-piston machines was, therefore, often pulsating and unsuitable for many purposes.

Furthermore, it is well known that the efliciency of prime-mover machines (e.g. internal-combustion and vapor-expansion engines) and energy-consuming machines (e.g. pumps and compressors), which operate with a compressible working fluid, is limited both by the dimensions of the inlet and outlet apertures for the fluid and by the volume swept out by the piston or pistons upon the expansion and contraction of the working chambers. Conventional reciprocable-piston compressors, pumps and engines are typical of machines whose efiiciency is so limited.

It is, therefore, the principal object of the present invention to provide a machine operating with a compressible fluid adapted to obviate the above-mentioned disadvantages of hitherto existing machines.

A more specific feature of the invention is to provide a radial-vane internal-combustion engine having a relatively uncomplicated linkage between the rotating pistons and adapted to operate with high efliciency and excellent fuel economy.

The above objects are realized, in accordance with the invention, by a machine comprising a common cylinder for at least two concentric pistons each having at least one or a plurality of angularly spaced radial vanes, preferably a pair of diametrically opposite vanes, adjacent vanes respectively belonging to the two pistons and forming between them a working chamber while being rotatable relatively to the cylinder, and a control linkage interconnecting the pistons for relative angular displacement about their common axis to contract and enlarge periodically the working chamber or chambers; the control linkage comprises a planetary gear rigidly connected with one of the pistons and meshing with a sun gear coaxial with the shafts thereof, and a connecting rod eccentrically journaled to the planet gear and pivotally connected to the other piston. Thus, upon a relative rotation of the planet and sun gears, the two pistons will be angularly reciprocated toward and away from one another to expand or contract the aforementioned working chambers. During the expansion of one of the chambers, therefore, a working fluid (e.g. a combustible mixture or a gas to be pumped) may be drawn into the chamber which, during the subsequent contraction thereof, is compressed and ignited or expelled under pressure therefrom.

Advantageously, the two sets of radial vanes are rigid with respective shafts journaled for rotation relative to the stationary cylinder and the planet gear, each shaft being provided with a respective radially extending guide member or arm. One of the arms carries the planet wheel, which is rotatably journaled thereto, whereas the free extremity of the other arm is pivoted to the connecting rod. The planet wheel is preferably assigned to the. leading piston, i.e. the piston whose vanes form the leading surfaces of the working chambers as the latter rotate together with both pistons about their common axis, the connecting rod having its pivot eccentrically located so a that the radially outward extremities of the arms are separated by a maximum distance when a working chamber is in the vicinity of the fluid inlet to the cylinder and by a minimum distance when the chamber is angularly displaced to a predetermined location of maximum compression of the fluid therein. Moreover, the eccentric pivot should be so positioned that, upon the ignition or expansion of a gaseous fluid in the working chamber at the location of maximum compression, a torque will be exerted upon the planet gear tending so to rotate it in engagement with the sun gear that the arm carrying the planet gear is displaced in the sense of rotation of the pistons about their axis upon an increase in the fluid pressure within this chamber tending to separate its two piston vanes. There is, therefore, substantially no tendency for the leading piston, which is advantageously connected to a suitable load, to be slowed in its rotation relative to the cylinder while the working chambers are alternately expanded and contracted. The kinematic disadvantages of conventional rotary-piston machines are thus obviated by the aforedescribed construction according to the invention wherein the control linkage, although relatively simple, may be extremely strong and is highly eflicient in its operation.

According to a more specific feature of the invention, the leading double-vane piston is of relatively large mass and may be constructed from a material having a relatively large specific gravity (e.g. cast iron) so as to have a large momentum whereas the trailing piston is constructed from a material having a low specific gravity (e.g. an aluminum or other light-metal alloy) and has a relatively small momentum. The leading piston, therefore, serves as a flywheel and rotates with a substantially uniform speed while the trailing piston, coupled to it via the control linkage, rotates together therewith at alter-.

nately slightly higher and lower speeds whereby the working compartments are periodically expanded and contracted.

Still another feature of the invention resides in the provision of means for rotating the sun wheel relatively to the cylinder, thereby advancing or retarding the contraction of a working chamber and shifting the location in the angular path thereof at which maximun compression is attained. If the cylinder is provided with, say, a spark plug for igniting a compressed combustible mixture within a working chamber, the degree of compression or the so-called ignition point of the fluid therein as the chamber sweeps past the spark plug may be regulated by angularly adjusting the sun gear. Silimarly, the degree of expansion and contraction of the working chama Patented Aug. 11, 1964 3 bers as the latter sweep past the inlet and exhaust ports may also be adjusted.

To achieve effective utilization of the volume of the working chambers in the face of different operating'conditions (e.g. different fuel types, humidity and temperature conditions) and to permit ready adjustment of the compression ratio (i.e. the ratio of the maximum volume of a working chamber to its completely contracted volume), I provide means for varying the maximum and minimum distances between the radially outward ends of the arms secured to each of the double-vane pistons. Advantageously, such variation may be carried out with the aid of means for increasing or decreasing the effective length of the connecting rod linking the two arms, the connecting rod then being provided with a telescopable extension, turnbuckle or the like for effecting the lengthening or shortening thereof. The effective length of the connecting rod may also be adjusted by regulation of the distance of its eccentric pivot from the axis of the planetary gear.

The control linkage, according to another feature of the invention, comprises means for periodically increasing the effective length of the connecting rod as the pistons rotate relatively to the cylinder whereby the normally limited volume of the working chambers may be increased in the vicinity of the inlet, thereby providing additional suction for the aspiration of a power fluid into the chambers, and the volume of the chambers in the region of the spark plug may be decreased by an equivalent amount to increase both the compression ratio and the operational efficiency of the machine. The connecting-rod linkage then may comprise a pair of connecting rod members, one of which is eccentrically pivoted to the aforementioned planet gear of the leading piston and is journaled to a follower planet wheel, which also engages the sun gear, while the other connecting-rod member is eccentrically pivoted to the follower or secondary planet gear and is journaled to the radial arm of the trailing piston. The follower gear thus periodically lengthens and shortens the effective length of the linkage constituted by the connecting-rod members as the two pistons rotate in the same sense relative to the cylinder.

The above and other objects, features and advantages of the instant invention will become more readily apparent from the following description, reference being made tothe accompanying drawing in which:

FIGS. 1-4 are cross-sectional views of a machine embodying the invention, taken along the line II of FIG. 7, diagrammatically illustrating successive. piston phases in the operation thereof;

FIGS. 1A-4A are cross-sectional views, taken along the line IA-IA of FIG. 7, diagrammatically illustrating the positions of the control linkage and corresponding, respectively, to FIGS. 14;

FIGS. and 6 are views similar to FIGS. 14 of a machine according to another embodiment of the invention;

FIGS. 5A and 6A are views similar to FIGS. 1A-4A and corresponding respectively to FIGS. 5 and 6; and

FIG. 7 is a cross-sectional view along an axial plane through the machine of FIGS. 14 with the pistons and control linkage substantially in the positions illustrated in FIGS. 3 and 3A.

In FIGS. 1-4, 1A-4A and 7 I show a cylindrical housing 1, which may be water-cooled in the conventional manner, provided with an inlet 2 for a combustible mixture 3 (eg a mixture of gasoline and air received from a carburetor) and an outlet 4 for exhaust gases, angularly offset from the inlet 2. The latter and the outlet 4 are provided with suitable valve means such as the slide valve 2 shown at the inlet 2 in FIG. 7. The cylinder housing 1 is also provided with a spark plug 6 at a location angularly offset from both the inlet 2 and the outlet 4 and arranged therebetween so as to lie beyond the inlet in the sense of rotation of a leading piston 8 and a trailing piston 7 journaled within the cylinder. The double-vane pistons 7 and 8 are formed with respective sector-shaped radial vanes 7', '7" and 8, 8", which extend axially substantially the full length of the cylindrical chamber enclosed by the housing 1 and just clear the peripheral and terminal Walls thereof. with sealing strips 9, bearing upon the inner surfaces of the closed cylindrical housing 1, which extend longitudinally along the curved outer surfaces of the sectorshaped vanes and radially along the flat end surfaces of these vanes confronting the terminal walls 1a and 1b of the housing 1.

The vanes 7 and 7" are diametrically opposite and rigid with a hollow shaft 10 projecting axially from the terminal wall In of the housing 1, a radially extending guide arm 11 being secured to the projecting extremity 10' of the shaft 10. To reduce possible strain on this arm, its radially outward or free end 11' carries a planetary idling gear 12 which meshes with a sun gear 16 coaxial with the cylinder housing 1 and the shaft 10. The diametrically opposite vanes 8' and 8" of rotary piston 8 are secured to the boss-portion 13b of a stepped shaft 13 whose portion 13a of reduced diameter passes coaxially through the hollow shaft 16 and forms a projection 13' extending axially beyond the shaft 16). The latter is journaled for rotation relatively to the shaft 13 upon a pair of axially spaced roller bearings ltla and 1012. A radial arm 14 is rigid with the projecting extremity 13' of the leading-piston shaft 13 and carries, at-its outer end 14, a freely rotatable leading planet gear 15 which will be further described hereinafter.

The hollow shaft 10 and the boss 13b of shaft 13 extend each over substantially half of the length of the cylinder chamber 1' and are co-extensive so that the vanes 7' and 7", secured to the shaft 10, axially overlie the boss 13b while the vanes 8 8" similarly overlie the shaft 10. The limited clearance between the inner surfaces of each set of cantilevered vanes and the shaft carrying the other set thereon is blocked by longitudinally extending strips 9 (FIG. 7) of sealing material on the undersurface of each vane.

The vanes 7', 7", 8 and 8" subdivide the cylinder chamber 1' into a pair of diametrically opposite working chambers A and B and a pair of supplemental or nonworking chambers C and D, the latter communicating with each other and being open into the atmosphere so that, upon a relative displacement of the two sets of piston vanes, there will be no substantial build-up of pressure in chambers C and D. To this end, the vanes 7' and 7 are formed with bores 7a opening into the chambers C and D (as shown for the chamber C in FIG. 7) which intercommunicate via a longitudinal channel 7b. The channels 7b in each vane 7', 7" are connected via bores 7c in the hollow shaft 11 with the common annular space between the shaft portion 13a and the hollow shaft 10 surrounding it. The annular space 100 communicates with the atmosphere via a plurality of angularly spaced bores 10d in the projection 10 of the shaft 10. A powertake-off gear 40 is fixed to the projecting end 13' of shaft 13 whereby the latter may be connected toa load, while a cam 41 is carried by the other end of the shaft to operate the fluid-controlling slide valves (e.g. valve 2') and to fire the spark plug 6 via a conventional, schematically illustrated valve linkage 42 and a spark controller 43. The cam 41 is adapted to close the valves as the chambers C and D sweep past the inlet 2 and the outlet 4, thereby preventing the escape of either the combustible mixture 3 or the exhaust gas 5 (FIG. 4) into the atmosphere via these chambers.

The sun gear 16, while normally stationary relatively to the cylinder housing 1, is connected thereto via countersunk screws, one of which is shown at 44, which engage arcuate grooves in the gear 16 and permit it to be angularly adjusted relatively to the cylinder upon a loosening of the screws. For a four-cycle engine having two work- The vanes are each provided ing chambers as illustrated, the diameter of the sun gear 16 should be twice that of the planet gear 15 engaged thereby which in turn, for convenience, may equal in size the idler gear 12 so that each working chamber will be expanded and contracted twice during each revolution of the rotary pistons.

The planet gear 15, whose guide arm 14 is rigidly connected with the leading double-vane piston 8, is fixed to a crank 18 whose free extremity 18' forms an eccentric pivot for one end 19" of an elongated connecting rod 19. The other end 19' of the latter is swingably connected to the outer extremity 11' of the guide arm 11 secured to the trailing piston 7. Thus, upon rotation of the leading piston 8 and the planet gear 15 connected thereto, the latter periodically displaces the trailing piston 7 relatively to the piston 8 to expand and contract the working chambers A and B.

The operation of the engine illustrated in FIGS. 1-4 and 7 will now be described with particular reference to the several positions of the control linkages, as illustrated in FIGS. 1A4A which correspond to the positions of the working chambers shown in FIGS. 1-4, respectively. As indicated in FIGS. 1 and 1A, the initial phase of the fourcycle engine is an aspiration of the combustible mixture 3 into the compartment A. Assuming that an initial rotation has been imparted to the pistons 7 and 8 in a clockwise sense (arrows 20) by means of a conventional starter motor, the sectoral working compartment A is swept past the inlet 2 whose valve 2' has been opened by the cam 41. Simultaneously, the clockwise-rotating planet wheel 15, meshing with the relatively stationary sun wheel 16, angularly displaces its crank 18 toward an initial dead-center position wherein the crank and the connecting rod 19 pivoted thereto are aligned and the outer extremities 11 and 14' of arms 11 and 14 are separated by a maximum distance (i.e. the sum of the lengths of the crank 18 and the connecting rod 19). The vanes 7" and 8" are thus progressively separated, thereby expanding the working chamber A as it sweeps past the inlet 2 to aspirate, say, a gasoline-air mixture from a carburetor into the chamber.

Continued rotation of the double-vane pistons 7 and 8, to displace the working chamber A containing the cornbustible mixture 3 through an angle of about 90, rotates the planet wheel 15 and its crank 18 past the initial deadcenter position, as indicated in FIGS. 2 and 2A, whereby the distance between the ends 11 and 14' of the arms 11 and 14 progressively decreases to reduce the volume of the working chamber A and to initiate compression of the power fluid therein. Further rotation of the pistons and their chamber A through an additional 90 (FIGS. 3 and 3A) displaces the chamber A past the spark plug 6 which initiates combustion of the mixture contained therein. Prior to ignition, however, the crank 18, rotated by the planet gear 15, has been displaced past its secondary deadcenter position, offset by an angle of 180 from the initial dead-center position, wherein the crank 18 and the connecting rod 19 extend parallel to each other in a common plane and the arms 11 and 14 have reached a position of closest approachwhereby the chamber A has been contracted to its minimum volume. Ignition of the mixture within chamber A when the linkage is in the position shown in FIG. 3A results in an explosive increase in the pressure within this chamber which, on the one hand, applies torque directly to the piston 8 tending to rotate in the direction of arrows 20 and, on the other hand, applies an oppositely effective torque to the trailing piston 7 which is transformed via arm 11 and connecting rod 19 into a torque effective to rotate the crank 18 and its planet gear 15 in a clockwise sense and to convert the rearwardly acting force of the expansion of the gases within chamber A into forces tending to displace the piston 8 in the clockwise direction, thereby also entraining the piston 7 against the countervailing forces acting thereon. The power of the fuel combustion is thus transformed into a rotation of the shaft 13 to drive the load and provides the momentum necessary for the compression of a new supply of power fluid which, simultaneously with the expansion of chamber A, is aspirated into the concurrently expanding chamber B.

The chamber A, upon a further rotation of about (FIGS. 4 and 4A), sweeps past the outlet 4, whose valve (not shown) has opened, while the crank 18 is again rotated past its initial dead-center position (shown in FIG. 4A) as the volume of compartment A is reduced to force the exhaust gases 5 therefrom. Continued rotation of the chamber A through an angle of about 90 returns it to the vicinity of the inlet 2 whereupon expansion of the chamber again aspirates the combustible fluid into it to continue the cycle of operation. While chamber A proceeds through the four-stroke phases of aspiration of fuel into the chamber, compression of the fluid therein, ignition of the compressed fluid and consequent expansion of the chamber to do work and to expel the exhaust gases therefrom, chamber B, diametrically opposite chamber A, proceeds through the identical sequence of phases in a cycle offset by an angle of from that of chamber A so that it is in a state of compression while chamber A is in a state of expansion and vice versa. Thus, two complete cycles of operation are accomplished upon a single revolution of the pistons 7 and 8.

. It will be understood that although the invention has been specifically described with reference to a single pair of Working chambers (A and B), the principles set forth are equally applicable to additional sets of working chambers. The chambers C and D may, for example, be used as working chambers in a two-stroke cycle, in which case there would be no interconnection between these two chambers or communication thereof with the atmosphere.

The present system, which has substantially no limitations as to the dimensions of the working chambers and the inlets and outlets, maybe used with only minor modification as a diesel engine. Thus, the spark plug 6may be replaced with a fuel injector operable when air within a working chamber is compressed to the ignition temperature of the fuel whereupon the latter is injected into the compression chamber. Angular adjustment of the sun wheel 16 relative to the cylinder 1 permits the compression ratio and the ignition point of the fuel mixture within the working chamber to be varied to suit any desired fuel. Moreover, the surfaces of the double-vane pistons 7 and 8 defining the working chambers A and B may be suitably profiled to produce any desired compression and ignition conditions within'the chamber.

While the invention has been found to be particularly suitable for internal-combustion engines, it is also possible to operate the double-vane rotary-piston machine herein disclosed with a passive power fluid such as steam, with omission of spark plug 6, or to use the machine as a compressor, supercharger or pump. Furthermore, with any type of motive fluid, one may immobilize the arm 14 instead of the cylinder 1 whereupon the gear 15 will rotate the gear 16 and the cylinder housing 1 secured thereto to operate a load connected to this housing. When, however, the pistons 7 and 8 rotate, as described above, the leading piston 8 is advantageously constructed from a material, such as cast iron, having a relatively high specific gravity so that the momentum of this piston produces a uniform rotation of the load shaft 13. The trailing-piston 7 should then be constructed from a sub stantially. lighter metal so that it may be readily recipro cated relatively to the uniformly rotating piston 8.

To permit a simple adjustment of compression ratio of the working chambers, the connecting rod 19 may comprise means, such as a conventional turnbuckle, for lengthening or shortening it. I have found, however, that it is preferable alternately to lengthen and shorten the connecting-rod linkage periodically, thereby increasing the volume of the working chamber when the latter is aspirating the combustible mixture into it and additionally compressing the fluid therein at its location of maximum pressure. In FIGS. 5, 6 and A, 6A1 show a conmeeting-rod linkage having a periodically variable elfective length and comprising two connecting-rod members 19a and 1%. Rod member 19a is pivoted to the radial arm 11 of piston 7 and eccentrically journaled at 12a to a planet wheel 12c. The latter is rotatably carried at the outer extremity of a radial arm 12b freely swingable concentrically with the shafts and 13. Rod member 191) is pivoted at one extremity to the arm 12b coaxially with the planet gear 12 and, at the other extremity, to the crank 18 secured to the planet gear which is secured via arm 14 to the leading piston 8 and, like the planet gear 12c, meshes with the sun gear 16. The eccentric 12a is adjustable relative to the axis of gear 120 whereby its throw may be varied.

As indicated in FIGS. 5 and 5A, which show the working chamber and the linkage in a position just prior to the ignition of the fuel 3, and FIGS. 6 and 6A, which show the chamber and linkage in the condition of maximum expansion of the chamber, the eccentric 12c periodically varies the effective length of the linkage 19a and 19b to increase the volume of the chamber upon the aspiration of a power fluid into it (FIGS. 6 and 6A) and to decrease the volume thereof during compression of the fluid prior to ignition thereof (FIGS. 5 and 5A). This construction, while permitting operation through the phases of the fourcycle sequence previously described, affords the possibility of using extremely large compression ratios with or without concurrent alteration of the capacity of the chambers.

The invention as described and illustrated is believed to admit of many modifications and variations deemed to come within the ability of persons skilled in the art and considered to be included in the spirit and scope of the invention as claimed.

I claim:

1. In a machine operable with a compressible fluid, in combination, a generally cylindrical housing provided with an inlet for said fluid and an outlet for said fluid angularly offset from said inlet, a pair of radial pistons journaled within said housing on the axis thereof for relative angular displacement'about said axis, said radial pistons defining a working chamber within said housing successively registrable with said inlet and said outlet, and linkage means interconnecting said pistons for angularly reciprocating at least one of them relatively to the other, thereby periodically enlarging and contracting said chamber, said linkage means includes a sun gear secured to said housing coaxially with said pistons, a planet gear meshing with said sun gear rotatably connected to one of said pistons, connecting-rod means articulated eccentrically tosaid planet gear for pivoted motion about an axis olfset from the axis of said planet gear by a distance less than the radius thereof and to the other of said pistons, and adjustment means for varying the effective length of said connecting-rod means, said adjustment means including a further planet gear meshing with said sun gear for periodically varying the effective length of said connecting-rod means, said connecting-rod means including a pair of rod members articulated to said arms and an eccentric carried by said further gear interposed between said rod members.

2. In an internal-combustion engine, in combination, a generally cylindrical housing provided with an inlet for a compressible combustible fluid and an outlet for said fluid angularly olTset from said inlet, a pair of radial pistons journaled within said housing for concurrent rotation in the same sense and for relative angular displacement about said axis, said radial piston defining at least one working chamber within said housing successively registrable with said inlet and said outlet and including a leading piston and' a trailing piston, and linkage means interconnecting said pistons for angularly reciprocating at least one of them relatively to the other, thereby periodically enlarging and contracting said chamber, said linkage means including a sun gear secured to said housing coaxially with said pistons, a planet gear meshing with said sun gear rotatably connected to said leading piston, and connecting-rod means articulated eccentrically to said planet gear and to said trailing piston, said connecting-rod means including a first rod member eccentrically journaled at one of its extremities to said planet gear, a further planet gear meshing with said sun gear journaled at the other extremity of said first rod member, and a second rod member journaled at an eccentric pivot to said further planet gear and articulatedly connected to said trailing piston whereby the effective length of said connectingrod means is periodically increased and decreased upon rotation of said pistons.

3. The combination according to claim 2, further comprising means for adjusting the throw of the eccentric pivot carried by said further planet gear.

4. A machine operable with a compressible fluid, comprising a generally cylindrical housing provided with an inlet for said fiuid and an outlet for said fluid angularly olfset from said inlet, at least two pistons coaxially journaled within said housing for concurrent rotation in the same sense and for relative angular displacement about their common axis, each of said pistons comprising a pair of diametrically opposite radial vanes forming with the vanes of the other of said pistons at least two diametrically opposite generally sectoral working chambers successively registrable with said inlet and said outlet, two coaxial shafts rigidly secured to each of said pistons, respectively, and projecting axially from said housing, each of said shafts being formed with a respective radially extending arm outwardly of said housing, a sun gear secured to said housing coaxially with said shafts, a planet gear journaled on one of said arms and meshing with said sun gear, connecting-rod means articulated eccentrically to said planet gear and to the other of said arms, thereby angularly reciprocating at least one of said pistons relatively to the other and periodically expanding and contracting said chambers, and means for periodically varying the effective length of said connecting-rod means including a further gear meshing with said sun gear and displaceable about the periphery thereof, said connectingrod means including a first rod member eccentrically pivotably connected to said further gear and articulated to one of said arms and a second rod member articulated to the other of said arms and to said further gear.

5. A machine according to claim 4, further comprising an idler gear meshing with said sun gear and journaled to an outer extremity of said other arm for supporting same.

6. A machine according to claim 4 wherein said planet and sun gears have a tooth ratio of 1:2.

References Cited in the file of this patent UNITED STATES PATENTS 309,734 Oehlmann Dec. 23, 1884 1,603,630 Morris Oct. 19, 1926 1,712,945 Thannhauser May 14, 1929 2,075,654 Martin Mar. 30, 1937 2,182,269 Whritenour Dec. 5, 1939 2,211,292 Ryerson Aug. 13, 1940 2,284,186 Wolstenholme May 26, 1942 2,349,848 Davids May 30, 1944 2,352,877 Wolstenholme July 4, 1944 

1. IN A MACHINE OPERABLE WITH A COMPRESSIBLE FLUID, IN COMBINATION, A GENERALLY CYLINDRICAL HOUSING PROVIDED WITH AN INLET FOR SAID FLUID AND AN OUTLET FOR SAID FLUID ANGULARLY OFFSET FROM SAID INLET, A PAIR OF RADIAL PISTONS JOURNALED WITHIN SAID HOUSING ON THE AXIS THEREOF FOR RELATIVE ANGULAR DISPLACEMENT ABOUT SAID AXIS, SAID RADIAL PISTONS DEFINING A WORKING CHAMBER WITHIN SAID HOUSING SUCCESSIVELY REGISTRABLE WITH SAID INLET AND SAID OUTLET, AND LINKAGE MEANS INTERCONNECTING SAID PISTONS FOR ANGULARLY RECIPROCATING AT LEAST ONE OF THEM RELATIVELY TO THE OTHER, THEREBY PERIODICALLY ENLARGING AND CONTRACTING SAID CHAMBER, SAID LINKAGE MEANS INCLUDES A SUN GEAR SECURED TO SAID HOUSING COAXIALLY WITH SAID PISTONS, A PLANET GEAR MESHING WITH SAID SUN GEAR ROTATABLY CONNECTED TO ONE OF 